1. Field of the Invention
The present invention relates to a seat structure in which a three-dimensional net having a large hysteresis loss is employed.
2. Description of the Related Art
Conventional automobile seats generally include spring members attached to a seat frame, a pad material such as a foamed material or cotton placed thereon, and a skin such as a vinyl leather, woven cloth, or leather covered thereon.
On the other hand, seats other than the automobile seats generally include a pad material placed on the frame and covered with a skin, and some of them also include spring members for enhancing the cushioning characteristics.
Although the spring members or the pad material acts to provide desired cushioning characteristics, conventional seats are mostly thick, heavy and costly.
In view of the above, a variety of lightweight, inexpensive and thin seats have been recently proposed, and the inventors of this application have developed thin seats having a lightweight net of a three-dimensional structure that is provided with desired characteristics (spring characteristics, damping characteristics and the like) sufficient for a cushioning material.
FIG. 5 depicts an example of the seat structures employing the three-dimensional net that has been developed by the inventors of this application, and particularly depicts a horizontal section of a seat back.
In the seat structure of FIG. 5, a three-dimensional net 52 stretched over a seat back frame 50 is selectively covered with a skin material 54. The skin material 54 is sewn on the three-dimensional net 52, to which is applied a predetermined tension by a plurality of tension members 56.
With this structure, because the three-dimensional net 52 is sewn together with the skin material 54 at a location where the back of a seat occupant is brought into contact with the skin material 54, this location is high in surface rigidity and, hence, expansion and contraction of the three-dimensional net 52 takes place at locations other than the central portion (the portion with which the back of the seat occupant is brought into contact).
Although the automobile seats employing the three-dimensional net are lightweight and have certain cushioning characteristics, they do not have a structure capable of selecting a riding feeling of being high in surface rigidity or a riding feeling in which the body of the seat occupant fits well with the seat and, hence, there is still room for improvement.